# [Pw_forum] Large shift of the Fermi energy - phonons, slab

Nicki Frank Hinsche nicvok at freenet.de
Sun Oct 27 19:04:33 CET 2013

```Dear community,

I am puzzled with some non-converging phonon calculations and
especially with a very large shift of the Fermi energy in the
perturbation step.
I am doing some calculations on metallic slabs, comparable to Eiguren
et al. Phys. Rev. Lett. (2002) vol. 88 (6) 066805 or
Hofmann et al. New Journal of Physics (2009) vol. 11 (12) 125005. It
worked out for several systems, with various thicknesses but now I
become
desperate calculating the phonons of a simple 21layer slab of Cu(111).
The vac. is around 2.5nm. The electronic structure looks fine, the
relaxation
is done - but the phonons fail for the Gamma point (only). The Fermi
energy shift is unphysically large. The DOS has no resonance nearby.

So what could be the problem? Any hints would be helpful.

Thanks Nicki

following some input/output for the phonons on (away) the Gamma point:

Input:

&inputph
reduce_io = .false.
tr2_ph=1.0d-12,
prefix='Cu',
alpha_mix = 0.150
ldisp=.true.,
nq1=4, nq2=4, nq3=1
start_q=1
last_q=1
recover = .true.,
amass(1)=63.546
outdir="***",
fildyn='Cu.dyn',
/

Output Gamma:

Computing dynamical matrix for.
q = (   0.0000000   0.0000000   0.0000000 )

7 Sym.Ops. (with q -> -q+G )
//
Atomic displacements:
There are  42 irreducible representations
//
Representation #  1 mode #   1

Self-consistent Calculation

Pert. #  1: Fermi energy shift (Ry) =    -0.1403E+01
-0.8470E-21

iter #   1 total cpu time :   168.5 secs   av.it.:   6.1
thresh= 0.100E-01 alpha_mix =  0.150 |ddv_scf|^2 =  0.277E+00
//
Pert. #  1: Fermi energy shift (Ry) =     0.1555E+08
-0.8882E-15
//
iter # 100 total cpu time :  2038.3 secs   av.it.:  25.3
thresh= 0.100E-01 alpha_mix =  0.150 |ddv_scf|^2 =  0.313E+15

And the output for a q-point away from Gamma:

Computing dynamical matrix for.
q = (   0.1443376   0.2500000   0.0000000 )

2 Sym.Ops. (no q -> -q+G )
//
Atomic displacements:
There are  63 irreducible representations
//
Representation #  1 mode #   1

Self-consistent Calculation

iter #   1 total cpu time :  1117.1 secs   av.it.:   5.8
thresh= 0.100E-01 alpha_mix =  0.150 |ddv_scf|^2 =  0.315E-04
//
iter #  15 total cpu time :  2442.8 secs   av.it.:  10.2
thresh= 0.105E-06 alpha_mix =  0.150 |ddv_scf|^2 =  0.454E-12

Some info on the self-consistent calculation before:

occupations='smearing', smearing='methfessel-paxton', degauss=0.01
ecutwfc = 38.0, ecutrho = 304.0,
conv_thr =  1.0d-10
K_POINTS {automatic}: 12 12 1 0 0 0
nat= 21, ntyp= 1
CELL_PARAMETERS {hexagonal}
0.86602540    -0.5000000   0.000000
0.86602540    0.50000000   0.000000
0.00000000    0.00000000   25.71450

-------------------------------------------------------------
Nicki Frank Hinsche, Dr. rer. nat.
Institute of physics - Theoretical physics,
Martin-Luther-University Halle-Wittenberg,
Von-Seckendorff-Platz 1, Room 1.07
D-06120 Halle/Saale, Germany
Tel.: ++49 345 5525460
-------------------------------------------------------------

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20131027/dfe7295d/attachment.html>
```

More information about the users mailing list